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The Fukushima Daiichi Incident – Dr. Matthias Braun - 04 June 2014 - p.10 The Fukushima Daiichi Incident 2. Accident progression 11.3. 15:41 Tsunami hits the plant Plant Design for Tsunami height of up to 6.5m Actual Tsunami height >7m Flooding of Diesel Generators and/or Essential service water building cooling the generators Station Blackout Common cause failure of the power supply Only Batteries are still available Failure of all but one Emergency core cooling systems

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The Fukushima Daiichi Incident – Dr. Matthias Braun - 04 June 2014 - p.11 The Fukushima Daiichi Incident 2. Accident progression Reactor Core Isolation Pump still available Steam from the Reactor drives a Turbine Steam gets condensed in the Wet-Well Turbine drives a Pump Water from the Wet-Well gets pumped in Reactor Necessary: Battery power Temperature in the wet-well must be below 100°C As there is no heat removal from the building, the Core isolation pump cant work infinitely

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The Fukushima Daiichi Incident – Dr. Matthias Braun - 04 June 2014 - p.25 The Fukushima Daiichi Incident 2. Accident progression Current status of the Reactors Core Damage in Unit 1,2, 3 Building damage due to various burns Unit 1-4 Reactor pressure vessels flooded in all Units with mobile pumps At least containment in Unit 1 flooded Further cooling of the Reactors by releasing steam to the atmosphere Only small further releases of fission products can be expected

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The Fukushima Daiichi Incident – Dr. Matthias Braun - 04 June 2014 - p.26 The Fukushima Daiichi Incident 3. Radiological releases Directly on the plant site Before Explosion in Unit Block 2 Below 2mSv / h Mainly due to released radioactive noble gases Measuring posts on west side. Maybe too small values measured due to wind After Explosion in Unit 2 (Damage of the Containment) Temporal peak values 12mSv / h (Origin not entirely clear) Local peak values on site up to 400mSv /h (wreckage / fragments?) Currently stable dose on site at 5mSv /h Inside the buildings a lot more Limiting time of exposure of the workers necessary

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The Fukushima Daiichi Incident – Dr. Matthias Braun - 04 June 2014 - p.28 The Fukushima Daiichi Incident 3. Radiological releases Outside the Plant site As reactor building mostly intact => reduced release of Aerosols (not Chernobyl-like) Fission product release in steam => fast Aerosol grows, large fraction falls down in the proximity of the plant Main contribution to the radioactive dose outside plant are the radioactive noble gases Carried / distributed by the wind, decreasing dose with time No Fall-out of the noble gases, so no local high contamination of soil ~20km around the plant Evacuations were adequate Measured dose up to 0.3mSv/h for short times Maybe destruction of crops / dairy products this year Probably no permanent evacuation of land necessary

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The Fukushima Daiichi Incident – Dr. Matthias Braun - 04 June 2014 - p.30 The Fukushima Daiichi Incident 4. Spend fuel pools Spend fuel stored in Pool on Reactor service floor Due to maintenance in Unit 4 entire core stored in Fuel pool Dry-out of the pools Unit 4: in 10 days Unit 1-3,5,6 in few weeks Leakage of the pools due to Earthquake? Consequences Core melt on fresh air Nearly no retention of fission products Large release

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The Fukushima Daiichi Incident – Dr. Matthias Braun - 04 June 2014 - p.31 The Fukushima Daiichi Incident 4. Spend fuel pools Spend fuel stored in Pool on Reactor service floor Due to maintenance in Unit 4 entire core stored in Fuel pool Dry-out of the pools Unit 4: in 10 days Unit 1-3,5,6 in few weeks Leakage of the pools due to Earthquake? Consequences Core melt on fresh air Nearly no retention of fission products Large release

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The Fukushima Daiichi Incident – Dr. Matthias Braun - 04 June 2014 - p.32 The Fukushima Daiichi Incident 4. Spend fuel pools Spend fuel stored in Pool on Reactor service floor Due to maintenance in Unit 4 entire core stored in Fuel pool Dry-out of the pools Unit 4: in 10 days Unit 1-3,5,6 in few weeks Leakage of the pools due to Earthquake? Consequences Core melt on fresh air Nearly no retention of fission products Large release It is currently unclear if release from fuel pool already happened

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The Fukushima Daiichi Incident – Dr. Matthias Braun - 04 June 2014 - p.33 The Fukushima Daiichi Incident 5. Sources of Information Good sources of Information Gesellschaft für Reaktorsicherheit [GRS.de] Up to date Radiological measurements published German translation of japanese/englisch web pages Japan Atomic Industrial Forum [jaif.or.jp/english/] Current Status of the plants Measurement values of the reactors (pressure liquid level) Tokyo Electric Power Company [Tepco.co.jp] Status of the recovery work Casualties May too few information are released by TEPCO, the operator of the plant